These human ecological concepts, i.e. the study of human relationship with environment made the later thinkers search the cause in environment. His advice in his treatise on "Airs, Waters and Places" elucidates vividly the role of environmental influences upon and relationships with human being in causing the disease.

HE RIGHTLY ADVISED TO SEARCH AIR, WATER AND PLACES FOR THE CAUSE OF A DISEASE.

It is the first scientific approach or reasoning regarding disease causation.

He loaded the gun of scientific thinking about disease causation while Pasteur, Henle, Koch and Pettenkoffer pulled the trigger.